焦

Phono-semantic compound:

火 (불 화) — semantic: fire, burning

隹 (새 추) — phonetic element, supplying sound

Thus originally “something burnt by fire,” later extended metaphorically to “inner burning,” i.e., anxiety or impatience.

焦心 (초심) — anxious heart, worry (rare; literary)

焦燥 (초조) — impatience, anxiety

焦土 (초토) — scorched earth

焦點 (초점) — focus, focal point

焦慮 (초려) — anxiety (modern CH→ often translated as 불안 in Korean)

焦眉 (초미) — “eyebrows burning,” i.e., urgent situation (焦眉之急)

Korean uses 焦燥 (초조) very frequently; “초조하다” is among the most common Sino-Korean emotional adjectives.

《孟子·梁惠王下》 (Mencius)

「民之憂在於飢寒，焦心於寇盜。」

“The people’s worry lies in hunger and cold; their hearts burn with anxiety over bandits.”

焦心 = “to burn with worry / be anxious.”

《漢書·食貨志》 (Book of Han)

「民不聊生，焦土千里。」

“The people could scarcely survive; a thousand miles were reduced to scorched earth.”

焦土 = “scorched earth”

《莊子·人間世》 (Zhuangzi, The Human World)

「焦然如喪考妣。」

“Burnt with anxiety as if he had lost his parents.”

焦然 = intensely worried.

《百喩經》 (Hundred Songs)

「如焦樹無枝葉。」

“Like a burnt tree without branches or leaves” — literal “burnt, scorched.”

《杜甫·北征》 (Du Fu's Northern Expedition)

「焦土千村空。」

“Across a thousand villages, only scorched earth remains.”